That link won't fix the problem because we don't use the wordpress cron feature, although ours uses a similar method.
The cron is triggered by hits to the site so you need hits for the schedule to run. That means that if you are using something like WP Super Cache, wordpress won't see any hits, they all go to the cache.
Another issue is that there might have been an error when the schedule ran. Processing the feed manually will tell you if there are any errors. You can also try enabling the debug log to see if that shows any errors.
There were some cron issues in previous versions (including v2.3 found in this forum) that occurred with some server configurations.
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